Thermal analysis of an inclined heat sink with finned PCM container for solar applications

Abstract

This paper explores the dynamic thermal performance of Phase Change Materials (PCMs) melting in an inclined finned rectangular container with the top heating mode. Internal external fins are provided to the back surface of the PCM tank considering its applications in the large duty cycle photovoltaic thermal management systems, top heating mode heat sinks and so on. Internal-external fins attached to the back surface of PCM container are proposed for: (a) to lengthen the melting time of PCMs during charging period specifically for peak sunshine hours in the solar applications (b) to enhance PCMs solidification during the discharging period and (c) to improve the heat transfer from the molten PCM to outside after complete melting; so as to reduce heat trapped. RT 42 is used as a PCM in the present study. Unsteady numerical investigations are performed with changing PCM thicknesses, inclination angles and number of extended surfaces. The PCM layer thicknesses are varied with 20 mm, 30 mm and 40 mm for the inclination angles of 30°, 45°, 60° and 90°. PCM container configurations with 2 fins, 3 fins and 4 fins are investigated. The effect of natural convection current is also included in the present numerical simulation using Boussinesq approximations. Control volume approach is used for the estimation of melting time, temperature distribution, velocity magnitude and Nusselt number enhancement. The result shows that the melting time for all the PCM systems increases with decreases in inclination angles and addition of a number of extended surfaces. The average PCM temperature and average velocity magnitude of the PCM decreases with decreasing inclination angle. Incorporation of additional fins than three does not add any significant enhancements in the melting time, although it drastically improves the PCM heat transfer performance. During the completion phase of melting process; using extended surfaces, Nusselt number is increased by 6–9 times for 30° inclined systems and 2–3 time with other inclination angles.